Hold-down apparatus for industrial trucks



Dec. 8, 1953 w, MGN T 2,661, 51

HOLD-DOWN APPARATUS FOR INDUSTRIAL TRUCKS Filed March 6, 1952 MIIIIJIHIIL [mm mm Joy/v W. Mc/Vurr,

Patented Dec. 8, 1953 HOLD-DOWN APPARATUS FOR INDUSTRIAL l TRUCKS John W. McNutt, Dravosburg, Pa., assignor to UnitedStates Steel Corporation, a corporation of New Jersey Application March 6, 1952, Serial No. 275,057

The present invention relates generally to industrial trucks and more particularly to automatically operating hold-down apparatus for preventing displacement of materials carried by industrial trucks.

Prior to my invention, stacks or piles of sheet material such as tin plate and the like were transported on conventional fork lift trucks. The material was loaded on the forks of the truck which were then elevated at sufficient distance above the mill floor to permit ready transport of the material. Since there is a strong tendency for steel sheets in a pile to slide on each other when being transported, it was necessary to weight down the top of the pile to maintain the sheets in a compact unit. This was usually done by applying pressure to the top sheet of the stack by means of manually operated screwdown plates or spring loaded plungers which were carried by brackets attached to the truck hoist mechanism. The operation of each of these types of hold-down devices was time consuming and each required manual manipulation-and adjustment for each load.

It is, accordingly, an object of my invention to provide a hold-down apparatus which functions automatically to apply pressure to the top of a pile of material being carried on the load carrier of an industrial truck to prevent dislodgement of the same. i I

It is a further object of my invention to provide a hold-down device for an industrial truck which automatically limits the operation of the hoisting mechanism of the truck when a predetermined amount of pressure is applied to the top of a pile of material being carried by the load carrier of the truck.

These and other objects will become more apparent after referring to the following specification and attached drawings, in which:

Figure l is a side elevation view, partly in sec-.

tion, showing the apparatus of myrinvention installed on the lower end of an industrial tractor; and

Figure 2 is a top plan View.

Referring more particularly to the drawings, reference numeral 2 indicates the loading end of an industrial truck of the conventional type having a load carrier which may consist of a pair of spaced lift forks- 4 attached to and disposed between a pair of spaced vertical side members 6 of the hoisting mechanism 8 of the truck. The load carrier is adapted to be lifted along the side members 6 by means of the hoisting mechanism 8 which consists of a chain 9 attached at 4 Claims. (Cl. 214-654) 2 7 one end to the back plate I! of the load carrier and at its other end to a rotatable chain drum I3. The chain drum is rotated by a reversing motor I5 through a worm gear connection ll. The motor i5 is actuated by a battery l9 through a circuit 2|.

The hold-down device of my invention, which I have indicated generally by the reference numeral i6, is attached to the upper portions of the members 6 by means of a pair of bracket arms I2 and a plate M which is attached to and extends transversely between the arms [2. A circular opening it is provided through the center of the plate l4 to accommodate a sleeve [8 which is welded or otherwise attached to the plate I 4. A plunger 26 is slideably fitted for axial movement within the sleeve it with its lower extremity 22 projecting through a retaining'ring 24 which is mounted around the inner Wall of the sleeve 58 adjacent its lower end tolimit the downward movement of the plunger. As shown in Figure l, the extremity 22 is of reduced cross sectional area and projects below the sleeve. I8. The projecting extremity 22 of the plunger 20 is internally threaded to receive a screw 26. A ball and socket connection 28 is provided at the end of screw 26 to hold a padded pressure plate 30 attached thereto. The ball and socket connection 26 permits self-adjustment of the plate 30 from the horizontal to conform with the slope of the sheet pile it bears upon. An adjusting lock nut is provided around the portion of the screw 26 between the end of the extremity 22 and the ball and socket connection 28 to secure the position of the screw.

A retainer plate 34 having a small hole 36 therethrough is bolted to the support plate [4 with the hole 36 being concentric with but smaller than the circular opening Hi. The hole 36 is provided in the plate 34 to permit passage of a rod 38 which projects vertically upward from the top surface of the plunger 28. A compression spring 40 is disposed within the sleeve I8 with one end bearing against the top surface of the plunger 20 to urge it constantly downwardly and its other end bearing against the retainer plate 34. A limit switch 42 having an actuating lever arm 44 is mounted on the retainer plate 34 with the lever arm extending over the hole 36 in the path of the rod 38. The rod 38 is positioned to contact the lever arm 44 and actuate the limit switch a 42 when the maximum upward travel of the plunger 20 has been accomplished. The limit switch 42 is provided withnormally closed contacts which permit operation of the hoisting mo-l tor l5. Contacting of the switch lever arm 44 by the rod 38 causes these contacts to open, thus interrupting the hoist motor current 2| and stopping operation of the motor.

In operation a pile of sheets W is loaded on the load carrier until the amount of material desired to ,be transported is in'the pile. The pile of sheets is then raised until the top sheet contacts the pressure plate 30 and causes the plunger 20 to compress the spring 40 and cause the rod 38 to contact the lever arm 44 and actuate limit switch 42. This stops the hoisting mechanism of the tractor as explained above, and the material is then ready to be transported.

The pressure applied by the plate 30 is sumcient to hold down the sheets and prevent them from sliding, but not enough to cause marking or scratching of the top sheet surface. The relative position of the plunger 20 at the time'the limit switch 42 acts can be adjusted by extending or decreasing the projection of the rod -38 from the top of the plunger.

. While one embodiment of my invention has been shown and described it will be apparent that otherladaptations and modifications may be made without departing from the scope of the followingclaims.

I claim:

'1. 'Inan industrial truck having lifting means on its forward end comprising a-pair of spaced vertically upright side members, a load carrier attached to and projecting forwardly between said members, and a hoisting mechanism for raising and lowering the load carrier along the side members, the combination therewith of-a bracket arm extending forwardly from the upper portion :of each of said side members in a plane above said load carrier, said arms-being in parallel relation to each other, a supporting plate having an opening therethrough attached to and extending transversely between said bracket arms, aresilient clamping member supportedby and depending from said plate above said load carrier for applying pressure on a loadcarried thereby, said clamping member including an elongated sleeve member mounted in said opening at one end and projecting downwardly therefrom toward said load carrier, a plunger slidably mounted for axial movementwithin said sleeve with one end projecting downwardly therefrom toward said loadoarrier, resilient means in said sleeve for urging said plunger downwardly toward said load carrier,- means for limitingthe downwardmovement of said plungerin said sleeve, a pressure plate attached to the projecting end of said plunger normal thereto for contacting the top of a load carried by'said load carrier, a rodattached to the upper surface of said plunger in said sleeve and extending upwardly therefrom toward said opening a limit switch having an actuating lever proa jecting therefrom mounted on said plate with said lever-disposed over said opening in the path of said rod, said switch being connected with said hoisting mechanism for controlling thesame, said rod being adapted to contact said leverarm to actuate said limit switch to stop the hoisting mechanism when the plunger of said clamping is moved upwardly by the top of a load beingcarried by said load carrier.

'2. In an industrial truck having lifting means on its forward end comprising a pair-of spaced vertically upright side members, a-load carrier attached to and projecting forwardly between said members, and a hoisting mechanism forraising and lowering theload carrier along the side memibers, the combination therewith of a bracket arm extending forwardly from the upper portion of each of said side members in a plane above said load carrier, said arms being in parallel relation to each other, a supporting plate having an opening therethrough attached to and extending transversely between said bracket arms, a retaining plate mounted over said opening in said supporting plate, said retaining plate having a relatively small hole therethrough in communication with the opening in said supporting plate, a limit switch having an actuating lever projecting therefrom mounted on said retaining plate with said actuating lever projecting over the hole in said retainer plate, a plunger slidably mounted for axial movement in said sleeve, a retainer ring mounted internally in said sleeve adjacent its lower end for limiting the movement of said plunger, a compression spring disposed in said sleeve with one end bearing against the upper surface of said plunger and its other end bearing againstsaid retainer plate, a reduced diameter portion integral with the bottom surface of said plunger having an internally threaded center bore therein and projecting outwardly of the lower end of said sleeve, an adjusting screw threaded into said bore with a portion thereof projectingfrom the lower end thereof, a pressure plate attached by ball and socket means .on'the projecting end of said screw, a lock nutthreaded on said screw adjacent the lower end of said .reduced diameter portion, a rod attached tothe upper surfaceof said plunger and extending upwardly therefrom throughsaid compression spring toward said actuating lever in line with the-openings in said plates, said rod-being adapted to 0011-. tact said lever arm to actuatesaid limit'switch to stop the hoisting mechanism when the plunger of said clamping member is moved upwardly as said pressure plate contacts the top of a load being carried by said load carrier.

3. In an industrial truck having lifting means on its forward end comprising a pair of spaced vertically upright side members, a load carrier attached to and projecting forwardly between said members, and 1a hoisting mechanismofor raising and lowering the load carrier alongthe. side members, the combination therewith of a :bracket extending forwardly from the upperportions-of said side members in a plane above said .'load.:car-. rier,- a vertically movable .clampingmember supported by said bracket above said load carrier and adapted to contact the top of a load carriedsby said load carrier and to .besmoved vertically up wardly thereby when said load is raised, means resiliently urging said clamping member toward said load carrier, a limit switch for controlling said hoisting mechanism, and means operatively associated with said clamping-member adapted to operate said limit switch tostop said hoisting mechanism when said clamping memberis contactingsaid load and has compressed saidres'ilient means a predetermined amount. 7

4. In an industrial truck having lifting means on its forward end comprising a pair of spaced vertically upright side -members, a loa dbarrier attached .to and projecting forwardly between saidmembers,- and a hoisting mechanism for raising and lowering the load carrier along the side members, the combination therewith of abracket arm extending forwardly from the upper portion of each of said side members in a plane above said load carrier, said arms being in parallel relation to each other, a supporting plate attached to and extending transversely betweensaid arms, a -vertically movable clamping member supported by said plate above said load carrier and adapted to contact the top of a load carried by said load carrier and to be moved vertically upwardly thereby when said load is raised, means resiliently urging said clamping member toward said load carrier, a limit switch for controlling said hoisting mechanism, and means operatively associated with said clamping member adapted to operate said limit switch to stop said hoisting mechanism when 10 said clamping member is contacting said load and has compressed said resilient means a predetermined amount.

JOHN W. McNUTT.

References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Rundle Aug. 14, 1917 Abbe Dec. 3, 1929 Murray July 1, 1930 Cochran Feb, 16, 1932 Hallenbeck Dec. 13, 1932 Sears Apr. 28, 1942 Reagle Aug. 29, 1950 

